Method of making a curved sealing element



E. J. RABSON July 22, 1969 METHOD OF MAKING A CURVED SEALING ELEMENTFiled May 31, 1967 United States Patent US. Cl. 29156.62 3 ClaimsABSTRACT OF THE DISCLOSURE A method of manufacturing a curved sealingelement for use in the side of the lobed rotor of a rotary pistoninternal combustion engine in which a straight strip of material of therequired cross-sectional shape is first produced and is subsequentlyformed whilst hot to the required configuration in which it is adaptedto be located in a curved groove formed in the rotor side.

This invention relates to rotary piston internal combustion engines ofthe kind in which a lobed rotor rotates in a chamber formed in ahousing. It is necessary to form a seal between the sides of the rotorand the housing and one object of the present invention is to provide animproved method of making a sealing element for use in this way.

In accordance with the invention a method of making a curved sealingelement for use with the lobed rotor of a rotary piston internalcombustion engine comprises producing a ferrous casting which issubsequently cut into strips to provide a plurality of blanks, machiningeach of said blanks to the required cross-sectional shape, placing eachblank in a jig to bend it to a curved configuration of open form andthen heating the jig and blank to set the blank in said curvedconfiguration.

The invention will now be more particularly described with reference tothe accompanying drawing in which FIGURES l and 2 are perspective viewsillustrating alternative steps in carrying out examples of a method ofmaking a sealing element in accordance with the invention and FIGURES 3and 4 are respectively a side view and a cross-section on the lines 4-4of FIGURE 3 of a jig which can be used in carrying out said method.

In one example of a method in accordance with the present inventionferrous material of a suitable composition is cast into a flat slab asshown in FIGURE 1 which is then cut in any convenient manner so as toform a plurality of straight strips of elongated configuration, the cutebeing indicated by dotted lines 11. Each strip thus formed is thenmachined whilst straight and in any convenient manner to the requiredcross-sectional configuration and is afterwards formed whilst hot to acurved configuration so that the curved strip is adapted to engage in acorrespondingly curved slot or groove formed in the side of a lobedrotor of a rotary piston internal combustion engine.

In forming a straight strip into the required curved configuration thestrip is bent to the required shape in any convenient form of jig and isthen placed in a furnace or oven which may have a neutral atmosphere.Such a jig may take the form shown in FIGURES 3 and 4, the jigcomprising an inner circular ring 12 together with a pair of arcuateclamping members 13 which can be detachably connected to the ring 12 bybolts 14. Thus two sealing elements (indicated by reference numeral 15)can be clamped in the jig between the ring 12 and the members 13 beforethe jig is inserted into the furnace or oven.

As an alternative to casting the ferrous material into a flat slab 10,as above described, the material may be centrifugally cast into the formof a hollow cylinder 16 (as shown in FIGURE 2) which is subsequentlydivided by a plurality of slits 17 each extending parallel to the axisof the cylinder so as again to provide a plurality of straight strips ofmetal which are then machined to the required cross-sectional shape,before being clamped in a jig and subsequently formed to a curvedconfiguration in a furnace or oven.

In use, a sealing element formed as above described may form part of amulti-elernent sealing system which provides a seal between the lobedrotor of a rotary piston engine and the associated housing in which saidrotor rotates. Thus for example where the rotor is of generallytriangular configuration the sealing system would include straightsealing strips fitted in grooves cut in the apices of the rotor, saidsealing strips mating with corner bolts housed in blind holes alsoformed in the apices of the rotor, and also curved sealing elementsformed as above described in accordance with the present invention,there being provided at least one curved sealing element between eachpair of adjacent corner bolts on each side of the rotor. Hithereto suchcurved side seals have been made by machining them from cast iron ringsand although this method of manufacture is satisfactory for use on smallengines, for larger engines it does not result in economicalmanufacture. This is because firstly it is necessary to machine the sealblank to the form of a short length of very thin walled large diametertube in order to reduce the weight of the seal as much as possible andsecondly the centrifugally cast cylinder providing the blank from whichthe rings are machined must be provided with an excessively largemachining allowance. With the present invention as above described anymachining is very readily effected whilst the sealing strip is in astraight condition and after the strip has been heat formed to therequired curvature no further machining is necessary with the possibleexception of reducing the length of the strip to provide the correctworking clearance in use.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. A method of making a curved sealing element for use with the lobedrotor of a rotary piston internal combustion engine, said methodcomprising producing a ferrous casting which is subsequently cut intostrips to provide a plurality of blanks, machining each of said blanksto the required cross-sectional shape, placing each blank in a jig tobend it to a curved configuration of open form and then heating the jigand blank to set the blank in said curved configuration.

2. A method as claimed in claim 1 wherein the ferrous casting is in theform of a flat slab.

3. A method as claimed in claim 1 wherein the ferrous casting is in theform of a hollow cylinder, a plurality of blanks being formed byslitting said hollow cylinder along lines parallel to its axis.

References Cited UNITED STATES PATENTS 1,303,896 5/1919 Hecht et al29-156.6 1,686,937 10/1928 Six 29-156.2 1,859,057 5/1932 Six 29-156.622,033,093 3/1936 Covert 29156.62 3,382,557 5/1968 Nickolaenko et al.29-l56.6

WILLIAM E. WAYNER, Primary Examiner US. Cl. X.R. 29-528

